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A boy who had large parts of the right side of his brain removed due to a slow-growing tumor made a nearly full recovery in the three years after his surgery, with other areas of his brain compensating for the loss, researchers reveal this week in Cell Reports.

Their case study highlights the brain’s tremendous ability to adapt to such losses and will help researchers better understand how, exactly, parts of the brain can accommodate such losses, the researchers write.

The boy, identified as UD in the case study, was a healthy, normal kid—up until he suddenly suffered a seizure at age four. He subsequently developed intractable epilepsy due to the tumor. When he was nearly seven years old, his parents and doctors made the tough decision to surgically remove the mass. That also meant removing the entire right side of his occipital lobe and part of his temporal lobe on his right side. Together, the extracted sections accounted for a third of the right hemisphere of UD’s brain.

The occipital lobe is one of the four major lobes of the cerebral cortex, the thick outer layer of gray matter covering our noggins’ hemispheres. The occipital lobe sits in the very back of the brain. It’s responsible for processing visual information from the eyes and linking the resulting images to memories. Both the right and left sides of the occipital lobe work together to process visual input, but the right side of the lobe handles input from the left side of our field of vision, while the lobe’s left side processes what we see in the right side of our visual field. The two sides of the lobe also have slightly different strengths in terms of visual processing; the right side is heavily involved in recognizing faces, while the left dominates in identifying written words.

The other lobe affected, the temporal lobe, is another of the four major lobes and borders the occipital lobe on the bottom of the cerebral cortex. This lobe processes auditory information and helps integrate memories with sounds and other sensory information.

After the surgery, doctors and researchers weren’t sure exactly how UD’s brain would handle losing such key visual and recognition regions. Of the two extreme possibilities, one was that his brain’s networks wouldn’t reorganize at all to compensate for the loss, and UD would have severe visual and sensory processing disabilities. The other extreme hypothesis was that UD’s brain would completely compensate, with other regions taking over the roles of the right sides of the occipital and temporal lobes, leading UD to function completely normally.

Bouncing back

The reality was much closer to full compensation. Missing the right side of his occipital lobe, UD’s brain never fully compensated for the loss of the region that handles visual input from the left side of his visual field. As such, he essentially has a permanent blind spot on his left side. He easily deals with this by simply moving his eyes and head to capture full peripheral vision on his left side, though.

The authors of the case report, led by cognitive neuroscientist Marlene Behrmann of Carnegie Mellon University, concluded that UD had not regained function in the “lower-order” visual cortex, meaning basic functions like peripheral vision. But, they note, he did regain all the more complex functioning in the “higher-order” visual cortex based on the results of more extensive testing.

In the three-year followup of UD’s recovery from surgery, the researchers tracked how his brain was functioning using fMRI—functional magnetic resonance imaging, which measures brain activity by monitoring changes in blood flow. They also had him take cognitive and perception tests.

As was the case prior to his brain surgery, UD scored above average on IQ tests and was within a normal range of visual perception for his age. UD performed just fine at recognizing faces, discriminating objects, perceiving global forms, and on reading-proficiency tests.

The fMRI results over the three-year followup indicated that the left side of his occipital lobe had continued to handle word processing while gradually reorganizing to pick up the slack on facial recognition—a task typically dominated by the right side of the lobe.

“The dramatic findings of essentially normal perceptual behavior and normal (albeit rearranged) neural correlates... attest to the power of plasticity of the higher-order visual system,” Behrmann and colleagues conclude.

While the surgery and reorganization was a triumph for UD—who has also been seizure free since the procedure—the researchers note his case raises a host of new questions. The largest being: what his recovery might mean for other patients. Was his young age critical for the reorganization? Would other children, if not adults, experience the same brain reorganization and compensation? Then, there’s the detailed molecular questions of how brain tissue pulls off such compensation—all important questions for more studies, of course.